Position error sensing and feedback apparatus and method

A position error sensing and feedback apparatus for a positioning device having a working piece which is moved along a rectilinear triordinate system of three mutually perpendicular axes, said apparatus comprising:

• (a) a reference laser source providing a highly polarized laser beam of a predetermined wavelength, said laser source being supported at a predetermined position relative said rectilinear positioning device, and said beam being directed substantially parallel to a first one of the axes of said triordinate system;
• (b) a first laser beam processing package located along said first axis for receiving said laser beam and comprising means for splitting said laser beam in order to permit the direction of a first portion thereof along a path substantially parallel to a second axis of said triordinate system, and to direct the remaining portion of said laser beam to at least one error detector means for measuring positional and orientational errors of said first processing package relative said laser beam;
• (c) a second laser beam processing package located along said second axis for receiving the first portion of said laser beam directed from said first processing package, said second processing package comprising means for further splitting said first portion of said laser beam in order to permit the direction of a second portion thereof along a path substantially parallel to the third axis of said triordinate system, and to direct the remaining portions thereof to at least one error detector means for measuring positional and orientational errors of said second processing package relative said first portion of said laser beam;
• (d) a third laser beam processing package located along said third axis of said triordinate system for receiving the second portion of said laser beam directed from said second processing package, said third processing package comprising means for directing portions of the second portion of said laser beam to a plurality of error detector means for measuring positional and orientational errors of said third processing package relative said second portion of said laser beam;
• and
• (e) feedback means for communicating the detected positional and orientational errors to a control unit of said rectilinear positioning device to enable correction of said deviation and to thereby provide improved positional accuracy of said working piece.

A positional and orientational error sensing and feedback apparatus for a positioning device having a working piece which is moved along a rectilinear triordinate system of three mutually perpendicular axes, said apparatus comprising:

• (a) a reference laser source for providing a highly polarized laser beam of a predetermined wavelength, said laser source supported at a predetermined position relative to and independent of said rectilinear positioning device, and said laser beam being directed substantially parallel to a first one of said mutually perpendicular axes;
• (b) a first laser beam processing package located on said positioning device along said first axis for receiving said laser beam, said first processing package comprising means for splitting said laser beam to enable direction of a first portion thereof along a path substantially parallel to a second one of said mutually perpendicular axes, another portion toward first detector means for measuring angular deviation and translation deviation of said first processing package relative said polarized beam, and another portion toward second detector means for measuring rotational deviation of said first processing package relative said polarized beam about the laser beam axis parallel to said first axis;
• (c) a second laser beam processing package located on said positioning device along said second axis perpendicular to said first axis for receiving the first portion of said laser beam directed from said first processing package, said second processing package comprising means for splitting said first portion of said laser beam to enable direction of a second portion of the beam along a path substantially parallel to the third of said mutually perpendicular axes, another portion toward third detector means for measuring angular deviation and translational deviation of said second processing package relative said first portion of the polarized beam, and another portion toward fourth detector means for measuring rotational deviation of said second processing package relative said first portion of said laser beam about its beam axis parallel to said second axis;
• (d) a third laser beam processing package located on said positioning device adjacent said working piece along said third axis perpendicular to said second axis for receiving the second portion of said laser beam directed from said second processing package, said third processing package comprising means for splitting said second portion of said laser beam to direct a portion thereof toward a fifth detector means for measuring angular deviations of said third processing package relative said second portion of said laser beam, a portion toward a sixth detector means for measuring translational deviations of said third processing package relative said second portion of said laser beam, and a portion toward a seventh detector means for measuring rotational deviation of said third processing package relative said second portion of said laser beam about its beam axis parallel to said third axis;
• and
• (e) feedback means for communicating the detected translational, angular and rotational deviations to a control unit of said rectilinear positioning device to enable correction of said deviations and to thereby provide improved positional and orientational accuracy of said working piece.

A method for detecting and correcting positional and orientational errors in a positioning device having a working piece which is moved along a rectilinear triordinate system, said method comprising the following steps:

• (a) directing a highly polarized reference laser beam of predetermined wavelength along a first beam axis substantially parallel to a first one of the axes of said triordindate system;
• (b) receiving said laser beam in a first laser beam processing package located along said first axis of said triordinate system, and processing said laser beam by splitting the same into a first portion which is to be directed outwardly from said first processing package along a path substantially parallel to a second axis of said triordinate system, and by directing the balance of said laser beam to error detector means for measuring positional and orientational errors of said first processing package relative said laser beam;
• (c) receiving said first portion of said laser beam directing from said first processing package in a second laser beam processing package located along said second axis of said triordinate system, and processing said first portion by splitting the same into a second portion which is to be directed outwardly from said second processing package along a path substantially parallel to the third axis of said triordinate system, and by directing the balance of said first portion to error detector means for measuring positional and orientational errors of said second processing package relative said first portion of said laser beam;
• (d) receiving said second portion of said laser beam directed from said second processing package in a third laser beam processing package located along said third axis of said triordinate system, and processing said second portion by directing the same to error detector means for measuring positional and orientational errors of said third processing package relative said second portion of said laser beam;
• and
• (e) feeding all of the positional and orientational errors detected at said first, second and third processing packages to a positioning device control unit to enable offsetting corrections to be made to said working piece.